Two train cars carrying carbon dioxide that derailed in Veazie on July 3 sit on the tracks behind Penobscot Plaza on July 6. A caller reported on July 6 that one of the cars (right) was making a loud hissing noise. Bangor fire crews were on scene for about 5 minutes, but were assured by railway officials that the hissing was part of "normal ventilation" to relieve pressure from the tanks on a warm day, according to fire department officials.

BANGOR, Maine — Railway and Bangor Fire Department officials said Saturday that the “hissing” coming from one of the tank cars that derailed a few days ago in Veazie is part of its “normal venting” and is not cause for concern.

Bangor fire and rescue crews were dispatched to the tracks behind Penobscot Plaza on Washington Street on Saturday afternoon after a caller reported an audible hissing sound coming from one of the two tanks parked behind the plaza.

Four cars derailed in a 92-car Pan Am Railways train on July 3 near the Veazie-Bangor town line. Three of the cars were carrying carbon dioxide and the fourth was empty, according to Pan Am officials. Two of those carbon dioxide tankers were parked behind Penobscot Plaza after a crane righted them and put them back on the rails.

Fire crews, including three trucks and an ambulance, were on scene for about 5 minutes Saturday, according to Assistant Fire Chief Thomas Higgins. As crews were on the way, Higgins was on the phone with a Pan Am representative who told him that the hissing was part of “normal venting,” in which a valve on top of the tank releases pressure. It’s especially common in warm temperatures, when pressure builds in the tank, he said.

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“Normally, it’s just not somewhere where someone would hear it,” the assistant chief said.

Higgins said he did not remember the name of the employee he talked to. The assistant chief also said Pan Am told him that no employees were immediately available to come out to reinspect the tanks, which had been examined and checked for leaks after the initial derailment.

The fire department examined the ventilation valves and dome on top of the tanks and found taht everything seemed to be operating correctly, Higgins said.

The Pan Am official also told Higgins that the company planned to offload the carbon dioxide into different tanker cars during the weekend for transportation.

The two cars parked behind the plaza on Friday showed signs of damage from sliding on their sides, and railings at each end of the tankers and on top surrounding the dome were badly bent.

A person who answered the phone at Pan Am Railways Operations Center in North Billerica, Mass., said “there’s nothing wrong with that car,” deferring further comment to a company spokesman who did not immediately respond to a message requesting comment.